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He will not be the official party nominee until the Republican National Convention

Mitt Romney hit his party's "magic number" on Tuesday, unofficially clinching the Republican presidential nomination in a race he entered as the front-runner and has had to himself for weeks.

Romney led the pack when he announced his second run for the White House last June, and he has watched his rivals for the nomination slowly trickle out as their own wins looked increasingly unlikely.

The delegates to put him over the 1,144 necessary for the GOP nomination came in Texas, the lone state to vote this week. Romney entered the day 78 delegates away from the magic number, and on Tuesday CNN projected he would win the state's GOP presidential primary, where 152 of the state's 155 delegates were at stake.

On Tuesday, Romney said he was humbled to have secured the requisite delegates to become the GOP nominee.

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"I am honored that Americans across the country have given their support to my candidacy and I am humbled to have won enough delegates to become the Republican Party's 2012 presidential nominee," Romney wrote. "Our party has come together with the goal of putting the failures of the last 3½ years behind us. I have no illusions about the difficulties of the task before us. But whatever challenges lie ahead, we will settle for nothing less than getting America back on the path to full employment and prosperity. On November 6, I am confident that we will unite as a country and begin the hard work of fulfilling the American promise and restoring our country to greatness."

The chairman of the Republican National Committee, Reince Priebus, congratulated Romney on the milestone, saying Romney would "offer America the new direction we so desperately need."

"Tonight, after six years of trying and millions of dollars spent, and after a year of tepid support against one of the weakest fields in history, Mitt Romney has finally secured enough delegates to become the Republican Party's presidential nominee," wrote Wasserman Schultz, the chairwoman of the Democratic National Committee. "Romney may have finally gained enough delegates to become the nominee, but what's been truly remarkable about his path to the nomination is how much damage he's left in his wake as he enters the general election."

Romney has been the presumptive nominee for weeks, but will not be the official party nominee until the Republican National Convention, set to be held the week of August 27 in Tampa, Florida.

Romney launched his campaign on a warm day last June, telling his supporters gathered at a New Hampshire farm that "Barack Obama has failed America."

"From my first day in office my No. 1 job will be to see that America once again is No.1 in job creation," he said.

The early primary battleground state would play an important role in his campaign. He initially invested more in New Hampshire than the first-in-the-nation caucus state of Iowa, which he eventually lost by a small margin to former Sen. Rick Santorum of Pennsylvania.

New England voters have long been familiar with Romney, even before his 2008 presidential bid. He served as governor of Massachusetts between 2003 and 2007.

Texas figured into this presidential race long before the first votes cast on Tuesday. One of the three factors in Santorum's April decision to end his presidential bid was a decision by Texas Republicans not to change their proportional delegate model to a winner-take-all system, which -- if he had stayed in the race and won the state -- could have given him a boost and held back Romney's delegate accumulation.

Two of Romney's rivals in the once-crowded field are from Texas. Texas Gov. Rick Perry exited the race two days before the mid-January primary in South Carolina after a disappointing fifth-place finish in Iowa and his decision to stop campaigning in the second state to vote, New Hampshire.

Earlier this month, Rep. Ron Paul of Texas said he would no longer actively campaign for the Republican nomination, effectively ending his third run for the Oval Office with 122 delegates.

When Santorum, Paul and others were still in the race, talk of a contested convention swirled and it seemed to some a realistic possibility that Romney might not reach the magic number before the last state voted in June.

Former House Speaker Newt Gingrich vowed to push his bid onward to the convention unless Romney were to clinch the nomination earlier. He told reporters in late March that if Romney "does not have a majority [of delegates], I think you'll then have one of the most interesting, open conventions in American history." He suspended his bid in early May, and on Tuesday was to appear with Romney at a fundraiser in Las Vegas.

The earliest contests weeded out Rep. Michele Bachmann of Minnesota, who won the Iowa straw poll last summer but finished sixth in its January caucuses, and former Utah Gov. Jon Huntsman, who ended his bid before the South Carolina vote after falling short in New Hampshire.

Others dropped out before the voting began. Businessman Herman Cain's once-unlikely rise ended in December amid allegations of sexual misbehavior. Former Minnesota Gov. Tim Pawlenty dropped out months earlier, in August, after the high stakes Ames, Iowa, straw poll.

Romney, who becomes the first Mormon presidential nominee of a major party, previously sought the GOP presidential nomination in 2008. He dropped out after Super Tuesday, which allocated 1,020 delegates from 21 states. The Texas primary in early March of that year gave Sen. John McCain of Arizona the necessary delegates to seal up the GOP nomination.

In his 2008 convention speech, Romney spoke about many of the same themes that are prominent in his campaign this cycle, including a call "to rein in government spending, lower taxes, take a weed wacker to excessive regulation and mandates ... pursue every source of energy security, from new efficiencies to renewables, from coal to non-CO2 producing nuclear and for the immediate drilling for more oil off our shores."

President Barack Obama faced no national competition for the Democratic presidential nomination, and CNN projected he accumulated the 2,778 necessary delegates on April 3.